The present invention relates in general to steam generators and, in particular, to a new and useful attemperator for steam generators which utilizes an annular opening centered around a steam passage to supply atomized liquid in the steam passage.
The use of water injection via direct contact spray attemperation apparatus to control steam temperature is well known in the art. Several designs for spray attemperators and nozzles are disclosed in Power, January 1986, pages 13-20, "How to put together systems for today's desuperheater needs", O'Keefe. FIG. 2 thereof discloses a conventional single orifice, non-adjustable spray nozzle. Steam flow is around the nozzle, and either a whirling action or a cone-shaped piece protruding part way into the orifice assists in atomization of the spray water.
FIG. 3 of the O'Keefe article discloses a variable orifice spray nozzle in which spray water supply pressure interacts with an opposing spring force in the nozzle to determine the position of a conical spray plug. Rather than focusing the spray water at a point, this design sprays the water outwardly in all directions. According to page 17 of the O'Keefe article, desuperheaters of this type are mounted to face upstream with respect to the direction of steam flow, delivering water into the steam, which turns the droplets around to carry them downstream and evaporate them.
FIG. 4 of O'Keefe discloses a combination of an external control Valve with a multiple-nozzle or orifice array to widen the turndown range of the device. FIG. 6 of O'Keefe is a variation of FIG. 4 where six spray nozzles are each fed by seven small orifices to further enhance turndown. In both designs, the valve stem extends down into the water tube located inside the steam carrying pipe and functions as a shutoff for the series of orifices. FIG. 5 of O'Keefe discloses an arrangement using multiple O'Keefe discloses the use of 10 to 20 orifice holes of varying sizes which are uncovered as an actuator raises the valve plug to expose the orifices.
FIGS. 8 and 9 of O'Keefe disclose the use of steam to enhance atomization of the spray water. In FIG. 8, a portion of the steam in the line flows through a Venturi section of the spray nozzle head itself to atomize the spray water which is introduced into the passage by a plurality of small orifices, rather than via an annular opening as in the present disclosure. FIG. 9 employs an external source of high pressure steam to shatter water being introduced into the steam flow. FIG. 10 of O'Keefe discloses a check-valve type of apparatus whose heavy plug, guided to prevent anything but limited vertical movement, rises and falls in response to the flow of steam. The floating plug design is also shown in another embodiment in FIG. 11, which uses a guide stem that also rises and falls in response to the steam flow. It should be noted that while an annular opening is provided in this device, it is the steam which passes through the annular opening, rather than the spray water.
The apparatus of FIG. 12, in O'Keefe, is again a steam conditioning type of valve, where the water enters the steam flow downstream of the valve seat and handles steam in a manner comparable to a cage-type PRV. FIG. 13 of O'Keefe is a low noise type in which multiple orifice holes are used, while the device of FIG. 14 of O'Keefe employs a contoured throttling plug to proportion the spray water in response to steam need.
U.S. Pat. No. 3,981,946 to Soya, et al, discloses an orifice forming member, having a slit and located in a Venturi section which encircles a central passageway. As steam flows through the central passageway, the Venturi effect pulls the water into the steam. In contrast to the present invention, the annular opening is in the walls of the pipe, rather than on the internal portion of a nozzle inserted into a pipe, and does not attempt to focus the water into a central portion of the central passageway.
U.S. Pat. No. 3,220,710 to Forster, discloses a self-regulating attemperator using a movable piston assembly which moves in response to steam pressure and which is quite similar to those described in FIGS. 11-14 of the O'Keefe article. However, while the water flows into the steam via an annular opening, the steam does not flow through a central passage around which the water is introduced at an angle to focus the water as in the present disclosure.
U.S. Pat. No. 4,442,047 to Johnson, and U.S. Pat. No. 4,130,611 to Brand, disclose multi-nozzle spray desuperheaters quite similar to those shown in FIGS. 4, 6 and 7 of the O'Keefe article.
U.S. Pat. No. 2,945,685 to Bowlus, and U.S. Pat. No. 4,071,586 to Seger disclose variable orifice desuperheaters. Bowlus utilizes a ball which is uplifted by the flow of steam off of its seat. As the ball is lifted, the high velocity steam passing by the water inlets to the device creates an atomizing action which serves to break up the water into fine droplets. Seger uses a cylindrical plug-type assembly slidably guided in a housing which is designed to be more compact in terms of space and use of material than previous designs.
U.S. Pat. No. 1,773,053 to McDermet discloses an arrangement of wire mesh and baffles introduced into the steam path and into which the spray water is introduced.
U.S. Pat. No. 4,011,287 to Marley discloses a labyrinth type of spray conditioning valve which injects the spray water upstream of the labyrinth disk stack.
U.S. Pat. No. 4,421,069 to Diggins discloses a desuperheater spray liner assembly supported inside a header of a steam boiler so as to accommodate longitudinal and radial expansion and contraction of the liner within the header.